This application is based on and claims the priority under 35 U.S.C. xc2xa7119 of German Patent Application 100 46 568.4, filed on Sep. 19, 2000, the entire disclosure of which is incorporated herein by reference.
The invention relates to a multi-pane window for an aircraft door, with an improved field of view from the inside to the outside of the aircraft, and especially in an area below the window, e.g. toward the bottom of the door.
The generally known construction of cabin windows in pressurized passenger aircraft is a double pane construction that provides fail-safe properties. A hollow interspace is enclosed between the outer and inner panes of the cabin window, and a ventilation or pressure compensation hole is typically provided near the bottom of the inner window pane in order to achieve a pressure compensation between the cabin interior and the hollow interspace between the window panes during flight, and especially during the climb and descent phases of a flight, which are typically associated with cabin pressure changes. It is also typically known that the perimeter or peripheral edges of the two panes are held and sealed in an airtight manner in a window seal, and are secured in a window frame which is in turn fitted into and mechanically connected to a corresponding opening in the aircraft fuselage.
Such a window construction for a passenger aircraft is, for example, disclosed in German Patent Publications DE 198 06 106 C1, DE 198 06 107 A1, and DE 198 06 108 A1. However, while this window construction is disclosed for a passenger cabin, it is not expressly mentioned for use in an aircraft door. For various reasons, different considerations apply to a window to be used in an aircraft door.
In the most modern passenger aircraft, in which the cabin floor is arranged rather high with respect to the cross-sectional contour of the fuselage, the windows are typically arranged at a location with a negative contour curvature of the fuselage. This is true also, or especially, for a window that is installed in an aircraft door of the aircraft, and results in a corresponding upward facing tilt of the window in the door. Such a result of the strong negative contour curvature of the door at the location of the window can be recognized, for example, in the known Airbus aircraft of the A319, A320, and A321 single aisle program series.
In order to ensure the safety of passengers who are to board or deplane through the aircraft door, both in the normal course of a flight and in an emergency evacuation situation, corresponding safety regulations require that the area outside of the door must be within view and visually inspected before the door is opened. For example, this means that a boarding stairway, boarding ramp or covered jetway that has been moved to the outside of the fuselage (in the usual situation), or an emergency evacuation slide that has been deployed (in an emergency situation), must be visible to the aircraft crew through the window of the door before the door is opened.
Due to the above described upward facing tilt of the windows, the field of view out through the window is limited, especially in a downward direction toward the area at the bottom of and below the door, where a stairway, evacuation slide, or the like would be arranged. For this reason, aircraft manufacturers have tried to improve the field of view through the lower portion of the window area, for example by arranging a thick heavy prism in this lower window area. Alternative attempts to improve the field of view in the lower window area have involved complicated mirror mechanisms or full solid lenses arranged to improve the view through the bottom area of the door window. Such prior art solutions have not been satisfactory, because they are costly, complicated, and do not provide a satisfactory improvement of the overall field of view.
In view of the above, it is an object of the invention to provide a window arrangement for an aircraft door, that provides an adequate field of view and adequate visibility of the surrounding area outside of the aircraft door, and especially to the area or fuselage section below the window, without interference or disagreeable distortion or limitation of the view, and in a simple economical manner. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a window arrangement for an aircraft door, comprising an outer pane and an inner pane that are sealed in an airtight manner by a window seal around the perimeter of the panes, and that are supported by a window frame in which the seal is received around the perimeter of the panes. An interspace is formed and enclosed between the two panes. Especially according to one embodiment of the invention, an intermediate pane embodied as an optical lens member is arranged within the interspace between the outer and inner panes, and is positioned and extends parallel to the surfaces of the outer and inner panes. The intermediate pane is embodied as an optical lens element over the majority, or especially substantially all of its surface, or particularly the entirety of its surface. For example, the intermediate pane is preferably embodied as a Fresnel lens over most or all of its surface. The Fresnel lens can be especially configured in such a manner to provide an increased field of view of the area below the window extending to the bottom of the door.
In an alternative embodiment, the lens element provided in the interspace between the outer and inner panes is embodied as a lens film that is adhesively bonded onto the surface of the inner pane facing the interspace. In a further alternative embodiment, the lens element comprises a lens configuration formed directly on the surface of the inner pane facing the interspace. The lens in each case is preferably embodied as a Fresnel lens.